/****************************************************************************
 *
 * Copyright 2017 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * drivers/bch/bchlib_read.c
 *
 *   Copyright (C) 2008-2009, 2016 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/
#include <tinyara/config.h>

#include <sys/types.h>
#include <stdint.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <debug.h>

#include "bch.h"

/****************************************************************************
 * Private Types
 ****************************************************************************/

/****************************************************************************
 * Private Function Prototypes
 ****************************************************************************/

/****************************************************************************
 * Private Data
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: bchlib_read
 *
 * Description:
 *   Read from the block device set-up by bchlib_setup as if it were a
 *   character device.
 *
 ****************************************************************************/
ssize_t bchlib_read(FAR void *handle, FAR char *buffer, size_t offset, size_t len)
{
	FAR struct bchlib_s *bch = (FAR struct bchlib_s *)handle;
	size_t		nsectors;
	size_t		sector;
	uint16_t	sectoffset;
	size_t		nbytes;
	size_t		bytesread;
	int			ret;

	/* Get rid of this special case right away */
	if (len < 1) {
		return 0;
	}

	/* Convert the file position into a sector number an offset. */
	sector     = offset / bch->sectsize;
	sectoffset = offset - sector * bch->sectsize;

	if (sector >= bch->nsectors) {
		/* Return end-of-file */
		return 0;
	}

	/* Read the initial partial sector */

	bytesread = 0;
	if (sectoffset > 0) {
		/* Read the sector into the sector buffer */
		bchlib_readsector(bch, sector);

		/* Copy the tail end of the sector to the user buffer */
		if (sectoffset + len > bch->sectsize) {
			nbytes = bch->sectsize - sectoffset;
		} else {
			nbytes = len;
		}

		memcpy(buffer, &bch->buffer[sectoffset], nbytes);

		/* Adjust pointers and counts */
		sector++;

		if (sector >= bch->nsectors) {
			return nbytes;
		}

		bytesread  = nbytes;
		buffer    += nbytes;
		len       -= nbytes;
	}

	/*
	 * Then read all of the full sectors following the partial sector directly
	 * into the user buffer.
	 */
	if (len >= bch->sectsize) {
		nsectors = len / bch->sectsize;
		if (sector + nsectors > bch->nsectors) {
			nsectors = bch->nsectors - sector;
		}

		ret = bch->inode->u.i_bops->read(bch->inode, (FAR uint8_t *)buffer,
						sector, nsectors);
		if (ret < 0) {
			fdbg("ERROR: Read failed: %d\n");
			return ret;
		}

		/* Adjust pointers and counts */
		sector    += nsectors;
		nbytes     = nsectors * bch->sectsize;
		bytesread += nbytes;

		if (sector >= bch->nsectors) {
			return bytesread;
		}

		buffer    += nbytes;
		len       -= nbytes;
	}

	/* Then read any partial final sector */
	if (len > 0) {
		/* Read the sector into the sector buffer */
		bchlib_readsector(bch, sector);

		/* Copy the head end of the sector to the user buffer */
		memcpy(buffer, bch->buffer, len);

		/* Adjust counts */
		bytesread += len;
	}

	return bytesread;
}
